As an ice making machine that automatically makes ice blocks, there is known a down flow type ice making machine in which an evaporation tube constituting a freezing system is arranged in a meandering manner at the rear surface of an ice making plate disposed approximately vertically, and ice making water is let to flow down the top surface of the ice making plate at the time a refrigerant is circulatively supplied to the evaporation tube to cool the ice making plate at the time of an ice making cycle, after which the cycle goes to a deicing cycle to separate and drop the ice blocks from the ice making plate.
At the time of the deicing cycle of the down flow type ice making machine, hot gas is circulatively supplied to the evaporation tube and deicing water of normal temperature is let to flow down to the rear surface of the ice making plate to heat the ice making plate, thereby melting ice forming surfaces between the ice blocks and the ice making plate, so that the ice blocks drop by the dead weight. The deicing water supplied to the ice making plate is collected in an ice-making water tank located under the ice making plate to be used as ice making water next time. An overflow tube is disposed in the ice-making water tank, that amount of deicing water collected in the ice-making water tank which is more than a prescribed water level prescribed by the overflow tube is discharged outside through the overflow tube.
In the down flow type ice making machine, when a temperature sensor detects that the temperature of a hot gas whose temperature rapidly rises as a result of separation of all of ice blocks in the deicing cycle has reached a preset deicing completion temperature, it is considered that deicing has been completed and control is performed to stop the deicing cycle and switch the cycle to the ice making cycle. In this case, the deicing water supplied to the ice making plate which is to be collected in the ice-making water tank at the time of the deicing cycle is set to become the prescribed water level before the time to the deicing completion temperature from the beginning of the deicing cycle, which is obtained in experiments or the like, i.e., before completion of the deicing cycle, in consideration of a variation or the like in the flow rate of the deicing water from the deicing water supply source. If the deicing water is kept supplied until the deicing cycle is completed, therefore, a large amount of deicing water is discharged wastefully, increasing the amount of water consumed. In this respect, there is a proposal to suppress the amount of wasted deicing water by stopping supplying deicing water to the ice making plate upon elapse of a supply time to collect deicing water whose amount does not make next ice making water insufficient in the ice-making water tank (see Patent Document 1, for example).
Patent Document 1: Japanese Patent Application Laid-Open No. 2006-64290